graham



July 16, 1963 A. B. GRAHAM F ORGING OF METAL ARTICLES Filed July 1, 1958 FIG.4

ATTORNEY United States Patent 3,097,420 FORGHJG 0F METAL ARTICLES Alexander B. Graham, Glasgow, Scotland, assignor to The International Nickel Company, Inc, New York, N.Y., a corporation of Delaware Filed July 1, 1958, Ser. No. 745,864 I Claims priority, application Great Britain July 25, 1957 2 Claims. (Ci. 29-1563) The present invention relates to the manufacture of metallic discs and, more particularly, to the manufacture of turbine rotor discs.

It is well known that turbine rotor discs and other metal articles can be forged from billets in presses, the billet being inserted in a cylindrical cavity or container which terminates in a radial extruding die of greater radius than the cavity and being deformed by a ram working in the cavity and forcing metal of the billet to flow substantially radially into the die. Now, in many billets as cast, there is a central core in which the metal grains have weak grain boundaries and this part of the metal is a source of a weakness in the finished product.

Although attempts were made to overcome the foregoing difficulty and other disadvantages, none, as far as I am aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that by the use of a special process, improved disc-like structures may be obtained.

It is an object of the present invention to provide a novel process for the production of disc-like structures.

Another object of the invention is to provide a novel process for the production of turbine rotor discs from heat-resistant metal.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawing in which:

FIGURE 1 is an external view of a cast billet as used in the present invention;

FIG. 2 depicts the billet of FIGURE 1 in a press during the first stage of the novel process of the present invention;

FIG. 3 shows the billet of FIGURE 1 in the same apparatus as shown in FIG. 2 during the second stage of the novel process of the present invention; and

FIG. 4 illustrates a disc-blank formed by the second stage of the process of the present invention in the apparatus as shown in FIGS. 2 and 3.

Generally speaking, the present invention contemplates a process for the production of discs including other disclike structures, wherein the central core of a billet is worked by performing the deformation of the billet to a disc in two stages. In the first stage, the central core is heavily worked and in the second, the remaining metal is more lightly worked. Thus, in the first stage of the production of a disc-like blank, the central portion of a metal billet is subjected to longitudinal deformation to induce the radial flow of metal while the billet is longitudinally confined and while a major portion of the billet adjacent the working tool is laterally confined. The second stage comprises subjecting the remaining portion of said billet to longitudinal deformation to continue the radial flow of said metal.

The invention may be carried out in an extrusion container opening on a die chamber with the use of two independently operable rams, namely, an inner cylindrical ram and an outer annular ram closely surrounding the inner ram. The inner ram is moved first and then the outer ram. The operation of both rams forces metal to flow radially in a die chamber at the forward end of the container.

In carrying the invention into practice, it is advanta- 3,097,420 Patented July 16, 1963 geous to subject heat-resistant metal to hot deformation in anapparatus as illustrated in the drawing.

Referring now thereto, the billet 11 shown in FIGURE 1 commonly has a central core 12 in which the grains have weak boundaries. The billet is placed in a cylindrical cavity in a press 13, this cavity leading to a die cavity 14-, designed to shape a blank for a turbine rotor disc. There are two rams, namely, an inner ram 15 and an outer ram 16. Advantageously, the inner ram has a crosssectional area of about 5% to about 15% of the crosssectional area of the cylindrical cavity. Initially, the billet has the length indicated by A and both rams make contact with its upper face. Then the inner ram is moved into the position shown in FIG. 2 while the outer ram is stationary. This causes some of the metal of the billet to flow into the die cavity 14 as shown in FIG. 2 and the central core is heavily Worked. Thereafter, the outer ram 16 is moved through the position shown in FIG. 3 and into the position shown in FIG. 4 in which its lower face is flush with that of the inner ram and more metal is forced into the cavity 4. In order to produce a turbine rotor disc from a product, i.e., a disc-blank, shaped as shown in FIG. 4, further forging may be applied. For the purpose of giving those skilled in the art a better understanding of the invention and/or a better appreciation of the advantages of the invention, the following illustrative example is given:

Example A cast billet of nickel-chromium alloy having a composition carbon ().1 max, titanium 1.'8-3.0, chromium 18-21, aluminium 0.8-2.0, silicon 1.5 max., manganese 1.0 max iron 5.0 max., cobalt 15-21, nickel balance, of cylindrical form 9" in diameter and of length 6 /2" was extruded using the rams 15 and 16 (FIG. 2), acting together as if they were a single ram with a flush leading edge, to produce a circular disc of 14%" diameter, 2 /2 thick. After machining and etching the surface of the disc centre weakness was seen to persist for some 6 percent of the cross-sectional area. This centre weakness derived from the original centre weakness in the cast billet.

A similar cast billet was then taken and extruded to produce a disc; the extrusion technique being such that the two rams, 15 and 16, were moved in the following manner:

(a) Ram 15 was moved first to work the centre portion of the billet under a load of tons while the billet was held in the container 13 by the ram 16. During this operation only a small amount of metal moved into the annular space 14 (FIG. 2).

(b) The metal of the nascent disc containing the now worked centre was held between the ram 15 and the bottom of the annular space 14 while it received further compression from the ram 16 under a load of 2250 tons. The diameter of ram 15 was 2". The resultant disc of 14 /2" diameter and 2 /2" thickness showed no signs of centre weakness carried over from the centre weakness in the billet.

The present invention is particularly applicable to the production of turbine rotor discs from heat-resistant metal. With respect to the manufacture of turbine blades by means of the novel process, it should be understood that the term heat-resistant metal is used to include austenitic nickel-chromium alloys, including nickel-chromium-iron and nickel-chromium-cobalt alloys, and cobalt-chromium alloys, including cobalt-chromium-iron alloys, which contain a total of at least about 25% nickel plus chromium, cobalt plus chromium or nickel plus chromium plus cobalt (i.e. a total of at least about 25 of chromium plus nickel and/or cobalt), in addition to small amounts of aluminium, titanium, molybdenum, tungsten, niobium,

tantalum, silicon, manganese, zirconium and boron with the balance iron, if any, which may optionally be present in the alloys. These alloys are adapted to be subjected in use to temperatures up to about 700 C. or above, and, accordingly, must be hot worked at temperatures around 1200 C.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. A process for the production of an improved disclike blank which comprises subjecting the central portion of a metal billet to longitudinal deformation to form a central cavity therein and to induce radial flow of metal adjacent one end of the billet while longitudinally confining said billet and while externally, laterally confining the major portion of said billet adjacent the deforming tool and thereafter subjecting the longitudinal end portion of said billet to deformation to continue the radial flow of said metal adjacent the same end of the billet and provide a disc having substantially the same volume as said metal billet and a greater diameter than said metal billet While maintaining the original lateral external confinement of said billet and while internally confining said 4 billet laterally by supporting the walls of said centnal cavity.

2. A process for the production of a turbine rotor disc blank made of heat-resistant metal which comprises pro viding a cast billet of heat-resistant metal, subjecting the central portion of said cast billet to longitudinal hot deformation by means of a deforming tool to form a central cavity therein and to induce radial flow of metal adjacent one end of the billet while longitudinally confining said billet and while externally, laterally confining the major portion of said billet adjacent the deforming tool and thereafter subjecting the longitudinal end portion of said billet to deformation to continue the radial flow of said metal adjacent the same end of the billet and provide a disc having substantially the same volume as said metal billet and a greater diameter than said metal billet while maintaining the original lateral external confinement of said billet and While internally confining said billet laterally by supporting the Walls of said internal cavity.

References Cited in the file of this patent UNITED STATES PATENTS 1,153,965 Singewald Sept. 21, 1915 1,382,734 Limont June 28, 1921 1,397,566 Walter Nov. 22, 1921 1,410,093 Dallmeyer et al Mar. 21, 1922 1,502,722 Hill July 29, 1924 1,568,061 Wilcox Dec. 29, 1925 2,305,803 Bayer Dec' 22, 1942 2,813,279 Friedman Nov. 19, 1957 

1. A PROCESS FOR THE PRODUCTION OF AN IMPROVED DISCLIKE BLANK WHICH COMPRISES SUBJECTING THE CENTRAL PORTION OF A METAL BILLET TO LONGITUDINAL DEFORMATION TO FORM A CENTRAL CAVITY THEREIN AND TO INDUCE RADIAL FLOW OF METAL ADJACENT ONE END OF THE BILLET WHILE LONGITUDINALLY CONFINING SAID BILLET AND WHILE EXTERNALLY, LATERALLY CONFINING THE MAJOR PORTION OF SAID BILLET ADJACENT THE DEFORMING TOOL AND THEREAFTER SUBJECTING THE LONGITUDINAL END PORTION OF SAID BILLET TO DEFORMATION TO CONTINUE THE RADIAL FLOW OF SAID METAL ADJACENT THE SAME END OF THE BILLET AND PROVIDE A DISC HAVING SUBSTANTIALLY THE SAME VOLUME AS SAID METAL BILLET AND A GREATER DIAMETER THAN SAID METAL BILLET WHILE MAINTAINING THE ORIGINAL LATERAL EXTERNAL CONFINEMENT OF SAID BILLET AND WHILE INTERNALLY CONFINING SAID BILLET LATERALLY BY SUPPORTING THE WALLS OF SAID CENTRAL CAVITY. 